4 TIKREDITY AND EVOLUTION IN PLANTS 



leaves appear above ground.^ The stem may be branched 

 or unbranched. When branched, the branches are pro- 

 duced without reference to the insertion of the leaves, 

 in contrast to the habit of higher plants of forming 

 branches only in the upper angle (axil) between the stem 

 and leaf-stalk. There is always a terminal btid at the 



). — A, Upper epidermis; B, lower epidermis of the leaf of the fern, 

 Drynaria meyeniana. (Camera lucida drawing.) 



tip of the fern-stem (and of the branches when any oc- 

 cur) ; and the leaves are usually attached just back of this 

 tip. The stems are commonly (though not always) 

 covered by hairs or scales (Fig. i), and on their older 

 portions, at some distance back from the tip, may be seen 

 the scars, or the ends of leaf-stalks, left by old leaves that 



' The leaves of ferns are often called fronds. 



